Separation of wax from residual lubricating oil



June 16, 1953A 111. DEFINITIONS From the foregoing discussion of prior art (II), it will be clear that a variety of terms have been applied to urea and thiourea complexes. The latter have been rather loosely described as double compounds, addition compounds, .difcult1y soluble compounds, Additions-Produkt, ad-

ducts, and crystalline molecular complexes.-

j thiourea plexors.

with other substances known in the chemical art.

Specically, adduct has been applied to Diels- Alder reaction products, formed by reaction of conjugated diolens and olens and their derivatives. As is well known, Diels-Alder products, as a rule do not revert to their `original constituents when heated or treated with water, acids, solvents, etc. Moreover, the term adduct has been dened earlier as The product of a reaction between molecules, which occurs in such a way` that the original molecules or their residues have long axes parallel to one another. (Concise Chemical and Technical Dictionary). Further ambiguity is introduced by the term adductionjf which has been dened as oxidation (Hackh).

To avoid the foregoing conflicting terminology, several related terms have been coined to define with greater specificity the substances involved in the phenomenon under consideration. As contemplated herein and as used throughout the specication and appended claims, the following terms identify the phenomenon:

Plexad-a revertable associated complex comprising a plexor, such as urea, and at least one other compound; said plexad characterized by reverting or decomposing, `under they influence of heat and/or various solvents, to its original constituents, namely, a plexor and at least one plexand.

Plexand-a compound capable of forming a plexad with a plexor, such as urea and thiourea.; compounds of this character differ in their capacity to form plexads, depending upon vario-us facto-rs described hereinafter.

Antiplex-a compound incapable of forming a plexad with a plexor. Y

Plexor-a compound capable of forming a plexad with a plexand; such as urea'and thiourea.

Plexate-to form a plexad.

Plexation--the act, process or effect of plexating.

IV. OUTLINE OF INVENTION It has now been found that the separation procedures used hitherto can be improved substantially by the use of certain solvents with a plexor.

As indicated above, urea plexadsand thiourea plexads have been formed by contacting a mixture containing a plexand and van antiplex, with urea or thiourea carried in water or an alcohol Plexation procedures of the foregoing character, however, are relatively ineicient, inasmuch as an appreciable quantity of an antiplex generally is occluded with the plexad and remains in admixture with the plexand when the plexad is decomposed. yThis is particularly pronounced in the treatment of lubricating oil stocks, from which waxes are removed by plexa- 1 tion with urea. In addition to this shortcoming, 10,

it has been noted that the waxes so separated from residual-type lubricating oil stocks have considerable color, thus making necessary additional processing to reduce the color of such A further shortcoming resides in the relatively low degree of selectivity of aqueous and alcoholic media which carry the urea and With such media., only relatively small quantities of waxes are removed from lubricating oil stocks. Another important consideration in the treatment of lubricating oils With urea for removing waxes therefrom is the desirability of a low pour point of the treated oil (antiplex). It has been found that treatment with aqueous and alcoholic media containing urea or thiourea often leads to a treated oil of relatively high pour point.

The shortcomings of previous plexation procedures have now been overcome by using pcresol, as the urea or thiourea solvent. In some manner, as yet not thoroughly understood, pcresol cooperates with the plexor to provide a more effective plexation.

V. OBJECTS It is an object of this invention, therefore, to

provide an effective means for separating hydro- Vto provide a substantially oil-free hydrocarbon wax characterized by a low degree o-f color. corresponding object is the provision of a lubricating oil substantially free of hydrocarbon wax and/or of appreciably lower pour point than the untreated lubricating oil stock.

Another object of this invention is to separate parain wax and microcrystalline wax from mixtures thereof. Still another object is to fractionate hydrocarbon waxes taining the same. Y Y

Another important object is the provision of a continuous method of separation `of said plexands and antiplexes, which method is ilexibile, capable of relatively sharp separation, and not highlyV demanding of attention and of utilities such as heat, refrigeration, pumping power and the like.

Other objects and advantages of the invention will be apparent from the following description.

VI. INVENTION IN DETAIL As indicated above, it has been found that the foregoing objects are achieved by plexation With urea or thiourea of a plexand or plexands, the urea or thiourea usedbeing carried in a medium comprising p-cresol.

(1) Pleands cmd mixtures suitable for plexatz'on The hydrocarbon mixtures and oxygen-con- Ataining parain mixtures mentioned in the disfrom mixtures con-A 5v cussion of the prior art, above, are contemplated herein. So also are the compounds, ple-xands, shown therein to have the capacity to form plexands. For example, when urea is usedr as a plexor, the mixture used may bef: isomeric cresols (Kremanm Schotte and Priewe); oestradiols (Priewe); lutidine-picolines (Riethoi); hydrocarbons containing straight chain hydrocarbons of at least six carbon ato-ms per molecule, and oxygen-containing mixtures containing straight chain acids, alcohols, aldehydes, esters and/or ketones having at least six carbon atoms per molecule (Bengen). It will be apparent fromv the definitions recited above, that the plexands of these mixtures are the compounds forming plexads with urea, and that the antiplexes` are the compounds which do not form urea plexads.

Hydrocarbon mixtures containing n-paraiins in the range of Cq-Cao and higher such as wax distillates, foots-oil, gas oils, virgin kerosenes, straight run naphthas are also suitable when urea is used as the plexor, such mixtures being shown in copending application Serial No. 4,997', filed January 29, 1948. Other mixtures shown in the latter application and also suitable here are: hydrocarbon mixtures containing n-pararlins and n-olens, and prepared by synthesis of carbon monoxide and hydrocarbons, i. e., typical Fischer Tropsch products prepared using cobalt and iron catalysts; cracked mixtures prepared by the vapor phase cracking of stocks rich in n-parains, such as by the cracking of paraffinic gas oils, foots-oil, crude waxes, etc.; mixtures containing straight chain oxygenated compounds, such as acids, alcohols, aldehydesl and esters, and containing branched compounds, such asthose obtained by synthesis with hydrogen and carbon monoxide over an iron catalyst or by oxidation of high molecular weight hydrocarbons; mixtures consisting essentially of n-parafhns and n-olefins, for the n-paraiins form stronger plexads than the n-olens; mixtures consisting essentially of n-olens with the double bond in various positions, for the olens having the double bond near the end ofthe chain form stronger'plexads than thosehaving the double bond further from the end of the chain; hydrocarbon mixtures obtained by isomerization, alkylation, dehydrocyclization, dehydrogenation, etc.

Other mixtures which may be more effectively plexated with urea by the present vprocess are those containing hydrocarbon derivatives and shown in application Serial No. 115,511, led concurrently herewith. Typical of the mixtures described in the latter application' are mixtures containing a straight chain halide having the halogen atom attached to a terminal carbon and having at least about ve carbons in the chain. Mixtures containing compounds characterized by a nitrogen-containing substituent, are also advantageously plexated with the present process; such mixtures include amines, amides, nitriles, nitroparains, etc. and are described in application Serial No. 115,515, led concurrently herewith. Sulfur-containing compounds present in various mixtures are also plexated eiciently herein; those are shown in application Serial No. 115,516, iiled concurrently herewith, now abandoned. Compounds containing cyclic substituents, present in various mixtures, are also efficiently plexated with urea in the present process, being shown in application Serial No. 116,593, led concurrently herewith. Plexation with urea of various terminally substituted compounds from mixtures containing: the; same and non-terminally substitutedcompounds, described in ap.- plication Serial No. 115,517, ledconcurrently herewith, is also-aided materially by the present process.

Urea plexation of a non-terminally mono-substituted compound from mixtures containing the same and a non-terminally poly-substituted compound, described in application Serial No. 115,513, led concurrently herewith, is also improved substantially by the present process. Similarly, more effective resolution with urea of mixtures containing parainic compounds of different degrces of unsaturation is realized herein; these mixtures are described in detail in applications Serial Nos. 115,514 and 115,518, filed concurrently herewith.

With regard to thiourea plexation, the mixtures shown in applications Serial Nos. 115,512 and 115,730, filed September 13, and 14, respectively, are suitable in the present process. In application Serial No. 115,512, highly branched parans and/or highly branched olens are separated from straight chain or less highly branched compounds. In application Serial No. 115,730, certain cycloparafns and/or cyclo-olens are separated from mixtures of the same and other hydrocarbons.

(2 PlewOfr The plexors used herein include urea and thiourea and, as indicated above, these plexors are used in solution in p-cresol. This solution should range from partially saturated to supersaturated at the temperature at which it is contacted with a plexand or with a mixture containingv one or more plexands and antiplexes. In many cases, it will be found convenient to suspend a further supply of urea or thiourea crystals in the solution, handling it as a slurry.

The solvent used is substantially inert to the hydrocarbons and/or hydrocarbon derivatives under treatment, and to urea or thiourea. It' is heat stable, both alone and in contact with the hydrocarbons, hydrocarbon derivatives, urea and thiourea, at temperatures at which the desired plexad is not heat stable.

p-Cresol can be used alone or with another solvent. It is oftenadvantageous to utilize a twocomponent system, as water and p-cresol. Solvents other than water and the phenols mentioned above, suitable for use in a multiple-component system, include alcohols, glycols, ethers, amines, polyamines, amides, acids, nitriles, etc. Typical of such solvents are: methanol, ethanol, propanol, ethylene glycol, butylene glycols, ethylene glycol dimethyl ether, triethylamine, hexylamine, piperidine, diaminoethane, diaminopropane, diaminobutane, formamide, formic acid, acetic acid, acetonitrile, etc. Such multiple-component solvents, partially staturated to supersaturated with urea or thiourea, lend themselves readily to a continuous process for separation by plexation.

Solutions containing suflicient water in order to minimize. the solubility of the hydrocarbons or hydrocarbon derivatives in the urea or thiourea solvent are often employed. The minimum quantity of water required depends upon the polarity andthe molecular weight of the hydrocarbon of hydrocarbon derivative (or plexand) being treated and, in general, this quantity will be greater with more polar plexands and with lower molecular weightcompounds.

Itis also contemplated` herein to include a small quantity of a surface active agent in the urea or thiourea solution, in the manner described in copending application Serial No. 115,437, filed concurrently herewith. v

Another modification contemplated herein is the procedure described in copending application Serial No. 137,739, filed January 10, 1950, involving contact of hydrocarbons and/or hydrocarbon derivatives with a plexor impregnated upon a porous support. In this modification, the solvents used with the hydrocarbon and/or hydrocarbon derivatives will be p-cresol as described herein.

An understanding of a preferred embodiment of this invention may be facilitated by reference to the accompanying illustrative drawing, Figure l, which is a schematic flow-diagram of one specie arrangement for practicing the invention.

In Figure 1, a mixture of hydrocarbons such as a waxy oil and a urea-p-cresol solution, is introduced through line i to plexation tank 2. The mixture in tank 2 is agit-ated for a suitable period of time, generally from several minutes to about three hours, at a suitable temperature, for example 125 F., in order to realize a satisfactory degree of plexation. It will be understood that plexation tank 2 is equipped with ya suitable stirrer or agitator (not shown). The resulting mixture is taken from tank 2 throughline 3, naphtha in line 4 is added to the mixture in line 3, and the composite is introduced into separator 5. Naphtha, such as a fraction boiling at 20G-300 F., is added to aid in separation of the urea-wax plexad, formed by piexation and antiplexes of the waxy oil. The separator can be a. centrifuge, lter, settler equipped with a suitable screw conveyor, etc., as will be understood by those skilled in the art.

Antiplex hydrocarbons, or oils, in admixture with some naphtha and p-cresol are withdrawn f from separator 5 through line 6; and urea-wax plexad, in admixture with some naphtha and pcresol, is withdrawn through` line 'I. An additional quantity of naphth-a is added through line to the material in line '1, and the resulting material is introduced to a second separator, 9, wherein further classification takes place. In separator S, antiplex hydrocarbons or oils are removed through line I0, and urea-wax plexad, together with some naphtha and p-cresol, is with-- drawn through line I I.

The urea-Wax plexad, in line II, is contacted with hot water (at about 150 F.) which is added through line I 2, and passed through heat exchanger I3 to separator I4. 'I'he heat exchanger I3 is maintained at about 150 F., such that the urea-wax plexad is decomposed or resolved. Wax is removed from separator I4 through line I5 and is introduced into fractionator I6. p-Cresol and naphtha removed Vthrough line I5 with the wax are taken to storage from fractionator I6 through lines I'I and I8, respectively, and wax is removed from the system through line IB. The wax so recovered can be further treated depending upon the use to which it is to be put.

p-Cresol recovered in fractionator IS and removed through line I? a-re stored in tank 2I, and can be recycled through line I. Similarly, naphtha taken overhead from fractionator It through line I8 is stored in tank 22, and can be recycled, as through lines 4 and 8.

From the separator I4, aqueous urea is taken through line 23 to a tower or still 24 wherein urea is concentrated. Water is removed from 24 through line 25, and a concentrated aqueous 8 urea is removed through line 25 and is taken through cooler 2l to line I for reuse.

Hydrocarbon oils, antiplexes, in lines 5 and I0, are introduced into fractionator 28 wherein naphtha and p-cresol admixed therewith are fractionated and are removed through lines 29 and 30, respectively. Recovered p-cresol and naphtha are stored in tanks 2I and 22, respectively, and can be recycled as indicated above. Hydrocarbon oils, or dewaxed oils, are removed through line 3 I.

As shown above, a urea-wax plexad can be decomposed or resolved to urea and wax, under the influence of water and heat. Plexads, by denition. can be so resolved, under the influence of heat and/or certain solvents, such as methanol, ethanol, water and others mentioned above. It is to be understood, however, that urea and thiourea plexads behave differently in various solvents. For example, urea-wax .plexads are soluble in isoarnyl alcohol and in pyridine at temperatures of about O-200 F., yand do not decompose under such conditions; however, they are recovered from such solvents by evaporation.

VII. ILLUS'IRATIVE EXALHPLES The following examples serve to illustrate, and not in any sense limit, the present invention.

A residual lubricating oil stock having the following properties was used in the illustrative examples:

Pour point, F. 80 SUV 210 F., secs 75.9 V. I. (approximate) 103 Color, Lovibond (1/4" cell) 115 Gravity, A. P. I. 28.5 Flash, ru 450 One part of oil was mixed with 1.9 parts (by weight) of a cresol and 0.8 part (by weight) of urea at F. (52 C.). The resulting mixture was maintained at 125 F. for 1/2 hour, and naphtha (20G-300 F. boiling range) was added to aid in the separation of plexad and antiplex. The plexad thus formed, comprising hydrocarbon wax and urea, was separated from the mixture by filtration, and the plexad lter cake was washed with additional n-aphtha. The plexad was then washed with hot water F.) to decompose the plexad, thereby setting free urea and molten WaX. The hydrocarbon .p1exand, Wax, was then separated by decantation. Similarly, the filtrate, or antiplex, was washed with hot water to remove urea therefrom, and naphtha was then removed by distillation.

Results of a series of examples with m, or oand p-cresols are set forth in the table below:

TABLE Run No l 2 3 Solvent p-Cresol o-Cresol m-Cresol Plexation Temp., oF 125 125 125 Agitation, Hrs. 1/2 Yields, Percent W Wax removed 4. 6 0. l 0

Oil remaining 90. 7 99. 2 89. 2

Loss 4.7 0.7 10.8 Properties of Wax: M. Pt.,

ASTM, F 149.4

Properties of Oil Remaining:

P. Pt., "F 55 90 105 SUV 210 F 85. 0 77. 9 77. 8

Color 180 190 250 Y Inspection of the data presented in the table reveals that p-cresol is an excellent solvent in cooperating with urea to reduce the pour point of the oil, and to provide a hydrocarbon wax of high melting point. In sharp contrast, however, are the results with o-cresol and m-cresol, inasmuch as there is little or no removal of wax and a no pour point lowering.

We claim:

In the refining of a residual lubricating oil stock containing hydrocarbon wax wherein said stock is contacted in solution with urea, whereby 10 said hydrocarbon wax preferentially forms a crystalline complex with said urea, and wherein said crystalline complex and the remaining oil stock are separated, the improvement which comprises: so contacting said oil stock and urea in solution in a cresol consisting of p-cresol, at a temperature of about 125 F. v

JAMES I. BARNES. ARNOLD O-. PUKKILA.

l() References Cited in the file of this patent UNITED STATES. PATENTS Number Name Date 1,830,859 Schotte et al Nov. 10, 1931 2,499,820 Fetterly Mar. 7, 1950 2,520,715 Fetterly Aug. 29, 1950 OTHER REFERENCES Technical Oil Mission, Reel 143, translations by Shell Development Co., of German patent application B 190,197, IV d 12, to Bengen, May 22, 1946, pages 2-6 only (5 pages). 

